Everything except Loki is weak to Ice, so make sure to bring some spells of that element. Enemies in this stage will not attack you physically, and will limit themselves to using a lot of ST and AoE Fire magic, as well as some ST Ice and Light magic for greater coverage. Any demon that can Null/Drain/Repel Fire while not being weak Ice or Light is an ideal option for this stage. Alternatively, you can just choose to use Makarakarn every turn to take away the first two enemy press turns with ease, although it will leave your weaknesses exposed after that. Since the Ice spells are ST only, you can probably get away with using demons weak to Ice, since there are a lot of those that can also void Fire spells.